Methods of moving a workpiece relative to a machine tool, and machine tools which are capable of movement relative to a workpiece are know in the art, for example, from EP 0 594 699 B1.
When workpieces are being machined on machine tools, there is the possibility, on the one hand, of moving the workpiece relative to a tool with a suitable drive in order to carry out machining of the workpiece. Alternatively, it is possible to move the tool relative to the workpiece. In some cases, moving the tool relative to the workpiece requires the movement of smaller masses than in the case of moving the workpiece. However, movement of the tool may be subject to limits if, for example, it is attached to a gantry which is moved over the workpiece. Such a gantry can be of a relatively great weight, and therefore the dynamics cannot be too high if there is to be sufficient accuracy. One solution which suggests itself, therefore, is to provide an additional, higher-dynamics drive which acts in the direction of a workpiece drive or a tool drive and which may only have to move very low weights, thereby enabling higher dynamics and greater precision to be achieved. For example, it is possible to provide on a gantry that is displaceable in a Y-direction by one drive a tool holder that is displaceable along the gantry by a relatively shorter distance in the Y-direction by a second drive. A tool held at the tool holder is thereby displaceable in the Y-direction by means of two drives. The first drive, driving the gantry, is frequently referred to as the machine axis and the second, higher-dynamics drive (which drives the tool holder), as the auxiliary axis. A drive that moves the workpiece in an axis direction is frequently referred to as the workpiece axis. The term “axis” is frequently used, therefore, to refer to the drive acting in the axis direction. The auxiliary axis may be a machine axis or a workpiece axis. The open-loop or closed-loop control of two drives acting in the same axis direction may, however, prove difficult.
EP 1 366 846 A1 proposes optimising machining of a workpiece with the aid of a computer program by determining, by reference to the contours to be machined, in the case of a laser cutting machine the contours that are to be cut, whether the gantry or only the tool holder is to be moved. In particular, the gantry can be positioned such that a maximum number of contours may be cut without it being necessary to move the gantry. Therefore, the cutting operation can be carried out solely by the auxiliary axis.
It is known from EP 0 594 699 B1 to supply a device with a control signal by a CNC control. The control signal indicates the required total movement to be executed. The device splits the signal into movement components of the tool support (lower-dynamics axis) and of an additional device (higher-dynamics axis). Apportionment to the two movement axes is performed by an electronic filter, the control signal components for the tool support being produced by a low-pass filter and the control signal components for the additional device being produced by a high-pass filter. Once the control signal has been apportioned, therefore, independent control of the drive of the tool support and the drive of the additional device takes place. The CNC control is supplied with feedback signals describing the total movement in an axis direction.